1. Field of the Invention
The present invention relates to an ink jet recording medium comprising a substrate and an ink-receiving layer provided on the substrate, more particularly such an ink jet recording medium for which the degree of cationization in the ink-receiving layer is controlled, and to a recording method for the ink jet recording medium, and an ink jet recorded article produced by recording an ink image on the ink jet recording medium.
2. Description of the Related Art
In the ink jet recording method, a discharge energy is applied to ink by using mechanical energy from a piezoelectric element or the like or thermal energy from a heat-generating body, thus discharging droplets of ink from a recording head onto recording paper and hence forming dots on the recording paper. This recording method has various good characteristics, such as recorded images being vivid, the driving apparatus being quiet, and it being easy to make color images, and has thus become more and more popular in recent years.
Known recording media for forming images (including writing) using the ink jet recording method include normal paper and also special ink jet recording paper having an ink-receiving layer on the recording surface side (front surface side). In recent years, it has come to be desired that vivid full-color images with yet higher resolution be formed on such recording media. With recent technical developments aimed at realizing high image quality, about the same high image quality as silver salt photographs has come to be demanded of ink jet recording media.
As described above, special ink jet recording paper generally has an ink-receiving layer, which contains a pigment and a water-soluble polymer such as polyvinyl alcohol. However, with an ink-receiving layer comprising such components, in the case that image formation is carried out using a water-soluble ink, the image formed has no water resistance, and hence the image quality is readily degraded.
To improve the water resistance of an image formed by attaching water-soluble ink onto the ink-receiving layer, art is known in which an organic water-soluble cationic polymer is used in the ink-receiving layer. Specifically, such ink-receiving layers are disclosed, for example, in Japanese Patent Application Laid-open No. S60-49990, Japanese Patent Application Laid-open No. S60-83882, Japanese Patent Application Laid-open No. S61-58788, Japanese Patent Application Laid-open No. S62-174164, Japanese Patent Application Laid-open No. H2-276670, Japanese Patent Application Laid-open No. H6-55829, Japanese Patent Application Laid-open No. H10-86508, Japanese Patent Application Laid-open No. H10-193776 and Japanese Patent Application Laid-open No. H10-217601.
However, although it is possible to confer a water resistance improving effect by making the ink-receiving layer contain a cationic polymer as described above, there are adverse effects on properties such as the ink absorbability and the light-fastness and colorability of images. In particular, in the case of colored inks, there may be large adverse effects on these properties due to differences in dye structure between the inks.
In particular, the dye molecules are larger in a cyan ink than a magenta ink or yellow ink, and thus tend not to penetrate easily into the ink-receiving layer. There is thus a tendency for the problem of ‘bronzing’ to occur in which the cyan dye agglomerates on the outermost surface of the ink-receiving layer, resulting in a drop in image quality. This tendency is particularly prominent with ink jet recording media having a glossy layer.
Moreover, the tendency of a cyan ink to discolor or fade more than a magenta ink or a yellow ink under acidic conditions or the presence of an oxidizing gas has been regarded as a problem from hitherto. With this in view, Japanese Patent Application Laid-open No. 2000-303009 discloses a cyan ink pigment for which this problem of cyan inks is resolved, specifically a novel copper phthalocyanine type pigment that is ‘gas-resistant’, i.e. resistant to discoloration or fading caused by oxidizing gases and the like.
However, even if a cyan ink containing the cyan pigment disclosed in Japanese Patent Application Laid-open No. 2000-303009 is used, the problem of cyan bronzing is not eliminated, and there is a tendency for degradation of image quality even with this cyan pigment.
To achieve high-quality color image formation, there are thus renewed calls for an ink jet recording medium that not only gives high ink absorbability, good colorability, and good water resistance, light-fastness and gas resistance, but also gives a low degree of ‘bronzing’.